Low Voltage Differential Signaling (LVDS) is a signaling technology that can operate at very high speeds over inexpensive, twisted-pair copper cables. LVDS transmits two different voltages which are compared at the receiver. LVDS uses this difference in voltage between the two wires to encode the information. More specifically, the LVDS output driver includes differential output terminals coupled to a current source that drives a differential pair of signal transmission lines. The basic input driver or receiver has a high DC input impedance, so that the majority of the driver current flows across a termination resistor. When the output driver switches, it changes the direction of current flow across the resistor, thereby creating a valid “one” (or high) or “zero” (or low) logic state.
Transition Minimized Differential Signaling (TMDS) is a signaling technology that is similar to LVDS in that it also uses differential signaling to reduce electromagnetic interference which allows faster signal transfers with increased accuracy. TMDS can be used to transmit high-speed serial data and is used by the Digital Visual Interface (DVI) specification and High Definition Multimedia Interface (HDMI) specification.
However, although LVDS drivers and TMDS drivers share some common features, they are structurally different and they operate under different operating parameters and have different operating characteristics. As such, depending on the operating environment, one type of differential signaling driver may be selected over the other type of differential signaling driver. Thus, a manufacturer may provide a communication device or circuit having both types of differential signaling driver. However, providing both types of differential signaling driver on a single communication device or circuit will significantly increase (e.g., double) the differential Input/Output (I/O) area, thereby consuming space on a die.